Translational Research of Hemoglobin-vesicles as a Transfusion Alternative

A fluid of hemoglobin-vesicles, Hb-V, is being developed as a transfusion alternative that comprises concentrated particle dispersion ([Hb] = 10 g/dL, occupied particle volume = 40%, particle size = 250 nm) with physicochemical characteristics comparable to those of blood. Encapsulation of a concentrated Hb solution with phospholipid vesicles can shield the toxic side effects of cell-free Hb. For facilitating translational research, we study efficient production methods, analytical methods, in vivo safety and efficacy of Hb-V. Recent results include (i) A new Hb encapsulation procedure has been established that enables a high yield and efficiency of Hb encapsulation for scale-up. (ii) Ferric metHb in Hb-V can be effectively reduced to the ferrous form in blood circulation by using the electron energies produced by RBC glycolysis via transmembrane electron mediators, phenothiazines, including methylene blue [1,2]. (iii) ADME of Hb-V and its minor effects on immunological system and hyperlipidemic condition are clarified [3,4]. (iv) Hb-V showed efficacies as a resuscitative fluid for uncontrolled hemorrhagic shock [5] and as a perfusion fluid for storing an amputated rat hind limb for replantation [6]. (v) Injection of CO-bound Hb-V is effective not only for resuscitation from hemorrhagic shock [7] but also for the treatment of idiopathic pulmonary fibrosis [8], presumably by the released CO that reduces generation of ROS. We also clarified that Hb-V can rescue placental hypoxia and improve fetal development in the rat pre-eclampsia model [9]. Through establishing the production method and confirmation of HbV safety and efficacy step-by-step, we prepare for the next stages of translational research. From the fiscal year 2015 this research has been supported by Japan Agency for Medical Research and Development (AMED). Our efforts continue aiming at eventual realization of Hb-V. References: [1] Sakai et al., Bioconjugate Chem. 25, 1301-10, 2014. [2] Kettisen et al., Bioconjugate Chem. 26, 746-54, 2015. [3] Fujihara et al., Artif. Organs 38, 234-8, 2014. [4] Taguchi et al., submitted. [5] Seishi et al., Shock 38, 153-8, 2012. [6] Araki et al., Transplantation 99, 687-92, 2015. [7] Sakai et al., Shock 31, 507-14, 2009. [8] Nagao et al., Biomaterials 35, 6553-62, 2014. [9] Li et al., Sci. Rep. 5, 15271, 2015.

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